easy pedal smooth mod

[Striker Amplification]

Speak the truth jimi!! pa-reach from-ah your book of ah-revelationssssssss-ah!!!!!!!

[R O Tiree]

You missed my point... Let's dissect this. I really would like you to answer these questions.

First off, what is a cross-over resistor? I'm not the only one to have asked.

Next, this is a basic LCR band-pass filter, as we've established. Why did you not give that information in the original post? It would have helped.

Please give us the values of the other components in your circuit. Capacitor, Tx specs and input impedance of what is next in the chain - then we can work out precisely what it's doing. Again, I'm not the only one to have asked. Primary is 7000 ohms, you said... purely a resistance reading at DC, or an impedance at a particular frequency? It matters. Ideally, we need both bits of info.

Why not just make a band-pass filter using something like a simple op-amp stage? It would be a lot cheaper, lighter and much more predictable, because it would neither depend upon, nor affect what happens downstream, except as you actually want it to do. Repeatably. Dependably. Every time.

If you are building purely for yourself, and you know what you are doing to a circuit, why you are doing it and how much it is going to change things in your signal chain, then that is entirely to the good. If you don't have a Scooby, but it works, then rock the f*** on. If, however, you are building "for fun and profit", even for mates, can you really afford to have unpredictable results? That's why I don't want to do it, incidentally. I'm interested in why it might work, though. To whit...

How is a 9VDC pedal, pushing out a few mW at best going to saturate a chuffin' great tube amp output Tx rated at 5W into an 8 ohm speaker?

This is, broadly speaking, jimi's approach - "I did this for sh!ts and giggles and it sounds really sick! I haven't really got the faintest what I just did though Why is it happening?" Then people come in, offer their opinions, insights or "Oh yes, I've seen that before, years ago in <xyz> pedal - it's because of <abc>" and everyone learns. Including jimi, whose knowledge has shot up dramatically, despite his claim about not caring what Ohm's Law is .

Now compare with yours - "Hey guys, I've just invented something that's never been done before!" without explaining how/why it works, no build photos, no sound clips, so most are somehow not really inspired to heat up our soldering irons. Then either try to bamboozle with confused and contradictory replies, go quiet, or get defensive when someone calls you on it and posts an almost identical schem. Or several of them, in one instance.

Let's face facts - we have ex-university profs here, been around since before a lot of this stuff was invented, in at least one case. We have professional electronics engineers, designing stuff that has got to work right, every time, for profit. We have people who design effects and build them for a living. We have inspired and inspiring tinkerers and hackers. We have people with an encyclopaedic knowledge of a huge number of different circuits and approaches, going from valve tech right up to DSP. This is not, in short, a group that can be bamboozled.

So, if someone posts a circuit, claiming originality, and it turns out to be a tweaked TubeScreamer, to use your analogy, then they are not going to get respect. They are, in the vernacular of the web, going to get owned.

And to address your last point, the circuit is used by plugging it into a guitar and an amp and trying to play a vaguely recognisable tune through it (at least in my case). As a designer/tinkerer, it helps to have at least a nodding acquaintance with what you're trying to achieve, though. Not essential, but it helps. Jimi gets respect, because he knows what he doesn't know and always thanks contributors for their time and effort in trying to work it out and explain it for all of us.

Now, if you would answer my questions, and those that others have asked in your other threads, then respect will be duly paid. Especially if it turns out that you don't fully know what you've done, merely that it works and 'fess up to that. And for Heaven's Sake - please post some clips, so we can hear what all the fuss is about.

Thanks in advance. And thanks for reading.

[Derringer]

does it really matter what power rating the transformer is and that the secondary is 8 ohm?

I'm thinking that it's the inductance value of the primary winding that matters here ... right?

[Jdansti]

> what is stopping everybody else from doing it?? i

One reason, probably not the only one, is the cost of copper. Long pieces of wire are many times more expensive than a handful of resistors and capacitors. Certainly many hobbiests who knock up a few pedals a year can afford the occasional  transformer, inductor, or choke, but as R.O. points out, just any ole' coil of wire ain't necessarily going to sound good, so you have to have the right one for whatever circuit you're working on. Most of us don't have a drawerful of various values of these components, and aren't going to spend $100 or more to stock up just to have some to try out. Now if we knew ahead of time exactly which part we needed and what it would sound like, We could order one or two and use them. The problem is that figuring this out is not a simple thing.

As for manufacturers, they're less likely to use these components unless its absolutely necessary, as in wah circuits.


Oh, and there's the issue of "bulk".

The issue of using inductors in stompboxes was discussed here: http://www.diystompboxes.com/smfforum/index.php?topic=101516.0.  R.G. and PRR provided some very useful information.

So inductors have their place, but people want to be assured of what effect it's going to have on the sound before they spend the extra cash.

[Striker Amplification]

yes exactly Derringer, the inductance value is what matters, i have no idea why you seem to think there is some major design flaw behind this, its simply a signal chain, the capacitor in the schematic was clearly from the effects output, you remove the 1/4'' jacks wiring from the output cpacitor, from the output cap one of the primary leads from the choke/output tansformer is then soldered, the other primary lead from the tranny carries on to 1/4'' jack's + terminal, that simple, as for a crossover resistor?- its a simple high reduction modification. As for an op amp simulation?? how in gods name is that a simple alernative? more room for a board, more components, and the wiring is 10x the complexity.....you tell me, -i dont go quiet man, i dont live on my computer, and i have already exsplained how this inductor works, it shifts frequency, it inverts your pedals output signal, the waveform entering the inductor is reversed, then reproduced backwards apon exit. an electrical engineering degree would tell you that

[Striker Amplification]

> what is stopping everybody else from doing it?? i

One reason, probably not the only one, is the cost of copper. Long pieces of wire are many times more expensive than a handful of resistors and capacitors. Certainly many hobbiests who knock up a few pedals a year can afford the occasional  transformer, inductor, or choke, but as R.O. points out, just any ole' coil of wire ain't necessarily going to sound good, so you have to have the right one for whatever circuit you're working on. Most of us don't have a drawerful of various values of these components, and aren't going to spend $100 or more to stock up just to have some to try out. Now if we knew ahead of time exactly which part we needed and what it would sound like, We could order one or two and use them. The problem is that figuring this out is not a simple thing.

As for manufacturers, they're less likely to use these components unless its absolutely necessary, as in wah circuits.


Oh, and there's the issue of "bulk".

The issue of using inductors in stompboxes was discussed here: http://www.diystompboxes.com/smfforum/index.php?topic=101516.0.  R.G. and PRR provided some very useful information.

So inductors have their place, but people want to be assured of what effect it's going to have on the sound before they spend the extra cash.

Radio shack , 5k DC choke $5.99

[artifus]

[armdnrdy]

Radio shack , 5k DC choke $5.99

I used different variations of Radio shack , 5k DC choke $5.99 on Radio Shack's site.......no hits.

I tried looking around under the keyword transformer...........no hits for anything as described by you.

Maybe I don't know how to use a search engine.     Got a link?

[Tony Forestiere]

I'm going out on a limb. I think we might be looking at a crude implementation of CA's original PassiveTC (without the cap switching). Craig's secret weapon: http://www.radioshack.com/product/index.jsp?productId=2103254#tabsetBasic
I can't directly link to the specification sheet, but it seems to stand up.

*Edit* Cheap inductor with tapped primary.

[earthtonesaudio]

yes exactly Derringer, the inductance value is what matters, i have no idea why you seem to think there is some major design flaw behind this, its simply a signal chain, the capacitor in the schematic was clearly from the effects output, you remove the 1/4'' jacks wiring from the output cpacitor, from the output cap one of the primary leads from the choke/output tansformer is then soldered, the other primary lead from the tranny carries on to 1/4'' jack's + terminal, that simple, as for a crossover resistor?- its a simple high reduction modification. As for an op amp simulation?? how in gods name is that a simple alernative? more room for a board, more components, and the wiring is 10x the complexity.....you tell me, -i dont go quiet man, i dont live on my computer, and i have already exsplained how this inductor works, it shifts frequency, it inverts your pedals output signal, the waveform entering the inductor is reversed, then reproduced backwards apon exit. an electrical engineering degree would tell you that

Sure has been a lot of discussion here for two components.
It's an LCR filter with the R's not shown, because they will be present in the things you hook up to the output and input.  Which brings us to the first reason this is not a common thing to put into a commercial effect pedal.  Its response is heavily dependent on the other elements the user brings to the table.  This will cause some users to say "sounds like X" and others to say "sounds like Y" simply because their setups are not the same.
Second, as others have mentioned: iron and copper are expensive, and relatively bad with economies of scale, at least compared to silicon.
Third: it can't be made adjustable very easily or cheaply.

I would say if you have the parts already then sure go for it.  Maybe it will be useful enough to build into a box with a switch etc.  But if I was building for mass production, or a modular system where you wanted to get "that sound" regardless of what effects preceded it or followed it, I would use an active filter.

Also I am 1 semester away from finishing my EE and I have no idea what that second-to-last sentence means.  Hope I didn't get ripped off.

[armdnrdy]

I'm going out on a limb. I think we might be looking at a crude implementation of CA's original PassiveTC (without the cap switching). Craig's secret weapon: http://www.radioshack.com/product/index.jsp?productId=2103254#tabsetBasic
I can't directly link to the specification sheet, but it seems to stand up.

*Edit* Cheap inductor with tapped primary.

Ah Ha......

I saw this one. It's not $5.99, and there is no mention in the spec sheet of it being rated at 5k.

I guess "an electrical engineering degree would tell you that"  

[artifus]

looks like i picked the wrong week to quit diystompboxes

[Striker Amplification]

keep it clean boys, dont lose your panties. I have absolutely no idea why such a simple "ancient" form is being dissected and looked at sideways like a picture of the mona lisa using a cell phone-

[induction]

the waveform entering the inductor is reversed, then reproduced backwards apon exit.

That's awesome! I didn't know you could do that without a flux capacitor. I'm definitely gonna build it. Then I'm gonna kill Hitler.

[Striker Amplification]

you know it must be great to log onto this site all day long and tell me how stupid iam guys, thats nice, and dont tell me it was not an attack by any means, once is fine but constantly?? im done here, since you like to pick people apart and exspose flaws for your entertainment.

[armdnrdy]

I believe that this is the basis for the "Completion backwards principle" as outlined by professors Fee Waybill, Bill Spooner and Roger Steen back in 1981.

[armdnrdy]

im done here

[CodeMonk]

I'm going out on a limb. I think we might be looking at a crude implementation of CA's original PassiveTC (without the cap switching). Craig's secret weapon: http://www.radioshack.com/product/index.jsp?productId=2103254#tabsetBasic
I can't directly link to the specification sheet, but it seems to stand up.

*Edit* Cheap inductor with tapped primary.

Thats the same one used in the Bobtavia I think.
Or some other octave/fuzz thingy.

This is whats on the box
impedancia :1khz 1v
entrada : 1 kohm +/- 10%
Frecuencia: 300-10,000 hz +/- 3db
Resistencia CD entrada: 70ohms +/- 20% salida 0.62ohm +/- 20%
Resistencia aislanted: 100Mohm 100Vcc

[Derringer]

i have no idea why you seem to think there is some major design flaw behind this,

I never even tried to imply that.

I'm just curious about the "why" and "how".

Like I said before, I understand the math behind an RC filter network and what type of rolloff occurs.
I'm curious how the rolloff would be different here with and inductor in series and in order to figure that out, I suppose I need to know the inductance of the coil ... now that you've confirmed for me that it is basically and inductor in series with the cap.

You said that it sounds different and I'd just like to to work it out on paper and compare to learn for myself.

[Striker Amplification]

the total resistance of the inductor is 7k(7,000) ohms